VAGINAL EPITHELIUM OF GUINEA-PIG 437 
succeeding stages were constantly contaminated by them, es- 
pecially in those obtained by means of a nasal speculum or a 
spatula; hence the value of the syringe method. 
As the process of cornifiecation continued, the cornified cells 
became loosened from the underlying layers and were cast off 
into lumen singly or in flakes of many cells. 
An interesting occurrence not described by any writer was the 
shedding of the entire cornified layer as a cast which showed the 
natural shape of the lumen of the vagina. It was possible in 
several animals by the use of the syringe to get several succeeding 
cornified casts at regular intervals of sixteen days. When pieces 
of the casts were examined under a microscope, the structure was 
readily recognized as continuous layers of superimposed cornified 
cells. Some very perfect casts were obtained, even showing the 
folds about the cervix. Fourteen complete cornified linings or 
casts were obtained and preserved, besides a great many more 
casts broken in the process of taking the sample. This shedding 
of the entire lining of the vagina occurred at the end of stage 2. 
The shedding of the entire cornified layer would seem to have 
been mistaken by Stockard and Papanicolaou to be the whole 
vaginal epithelium separated from the underlying connective tis- 
sue, for, according to them (719, p. 234), “the epithelium is now 
expelled as one continuous tube forming the cover around the 
vaginal plug instead of sluffing off in smaller pieces as occurs dur- 
ing the fourth stage when copulation has not occurred. However, 
the vaginal epithelium may occasionally be shed en masse without 
copulation. . . . . Itisclear, therefore, that what was termed 
by Lataste the ‘enveloppe vaginale’ is the layer of epithelium 
separated from the underlying connective tissue. ae 
That the entire vaginal epithelium did not separate froin: the 
connective tissue, but that only the whole cornified layer became 
loosened from the underlying epithelium and lay free in the 
lumen, is shown in figure 5. The condition of the vaginal epi- 
thelium immediately after the shedding and expulsion of the 
cornified cast is shown in figures 6 and 11. 
